You can get laser jammers, but they are expensive and I think they are illegal (or soon to become illegal).
I personally have a Garmin i3 GPS system with downloaded speed camera database. It lists pretty much all speed camera's plus common temporary speed camera spots etc and it works well.
The updates to the database are every one - two weeks so it is quite good. The government are also being "very" careful about how many new speed camera's they put in place nowadays because of the public perception of them as a stealth tax and therefore there are very few new camera's being put in, so usually a speed camera detector is pretty much up to date for a long time except for the odd few.
Also, if you are keeping a good speed and not excessively breaking the speed limit for the majority of the time, then you won't have to worry much.
My Garmin is cheap as chips, it was only £199 when I bought it and that was last summer, so it will be even less now and the speed camera updates are free or £2 a month dependent on where you go online to get them.
Of course a speed camera detector should "only" be used as an aid to tell you where they are located, it should not be used for you to do 60mph in 30 limits and be safe in the knowledge that it will pick up every single speed camera and warn you about it anyway!
No speed camera detector is perfect and no speed camera database is ever fully up to date (even the governments own database can be upto 4 weeks out of date).
At the end of the day, does it really warrant spending £300 - £400 on a speed camera detector that will do pretty much the same job as a GPS system for ~£150, but without
the addition of GPS navigation features.
And as stated already, laser detectors are nigh on useless, the only time they tell you about it, is usually
when you have just been stung by one!
Hope that helps a bit